The present invention relates to a film thickness measuring apparatus utilizing fluorescent X-rays.
In order to measure the thickness of a minute area using fluorescent X-rays, collimators have been used as means for illuminating a minute area of an object with primary X-rays for excitation. Among various kinds of collimators, a suitable one is selected according to the size of the object to be measured. Collimators are made generally in a circular or rectangular form. However since a collimator with a small aperture cannot pass an X-ray beam of sufficient intensity, a rectangular collimator has been used in order to obtain higher X-ray intensity for an elongated measuring portion.
When a rectangular collimator is used for a measurement, a sample object is arranged so as to orient perfectly a long and narrow portion to be measured with the long dimension of the collimator aperture.
A prior art rectangular collimator can obtain stronger X-ray strength. However there has been a disadvantage in that the workability is very bad in actual measurement. For example, a sample must be arranged in such a manner that a longer side of its measuring portion is matched perfectly with the long side of the collimator aperture, or if a sample has measuring portions oriented in different longer directions, a procedure must be repeated to match rotatably the longer side of a measuring portion with the long side of the collimator aperture.